Implantable prosthetic devices have been used in numerous locations in the body. The most common use has been for restoring or improving upon normal body contour or augmenting as well as reconstructing the female breast. The most common breast prosthesis is similar to that disclosed in U.S. Pat. No. 3,293,663 to Cronin, in which there is a flexible elastomeric container, typically silicone rubber, which is filled with a soft gel, typically silicone gel or a saline solution or a combination of both.
It is known that when a prosthetic device, including the Cronin type device, is implanted in the body, scar tissue totally encapsulates the device. This encapsulation leads to a problem of spherical scar contracture. As the scar tissue surrounds the prosthetic device it tends to contract, thereby causing the gel filled sac to assume a minimum surface area to volume configuration or spherical configuration. The problem of spherical scar contracture causes the breast implant to change from a shape approximating that of a natural human breast to that of a tennis ball.
Numerous solutions to the spherical scar contracture problem have been posed. A number of essentially structural and mechanically oriented devices have been proposed for amelionation of this problem. A number of these references are reviewed in the Background of the Invention section of my U.S. Pat. No. 4,955,907, the disclosure of which is incorporated herein by reference. Generally, these structural/mechanical approaches have proved unsatisfactory.
More recently, the use of a covering for implants having a plurality of defined regions which serve to disperse or disorganize the scar tissue have been disclosed. For example, in my U.S. Pat. No. 4,955,907, a variety of embodiments are disclosed which promote the dispersion or disorganization of scar tissue, among other ways, by providing defined boundaries for such tissue. It has been recognized that utilizing covering materials having highly and variables texturized surface, including microtexturized surface, promotes enhanced fixation of tissues to the implant, while reducing the region over which the undesirable scar tissue may pool and form.
A number of references have suggested various techniques for generating a texturized or microtexturized surface for the covering of the implant. One technique, described for example in Ersek et al, U.S. Pat. No. 4,944,909, is to include specific molecules whose shape and size produce 3-dimensional projections of from 20 to 500 microns in size from the exterior surface of the covering for the implant. Prior to vulcanization of the silicone rubber covering, the molecules are thrust onto the exterior surface with sufficient force to alter the surface morphology. A second technique is described in Patents to Cox U.S. Pat. No. 4,859,712 and Quaid U.S. Pat. 4,889,744. Both references disclose a technique of manufacturing texturized silicone rubber surfaces by applying particles or crystals to the external surface of the implant before it is cured, curing the external surface layer with those solid particles or crystals embedded in the surface, and then dissolving the crystals or particles with a solvent which does not dissolve the silicone rubber. A third set of techniques is disclosed in Yan et al U.S. Pat. No. 4,960,425. Generally a number of the disclosed techniques relate to the use of covering a silicone rubber layer with a porous or textured medium and pressing that medium into the silicone rubber until a texturized surface is formed in the silicone layer. Embodiments are described where the silicone rubber is in a disk form and where the silicone rubber surrounds a mandrel. An additional embodiment is described in which a mandrel has a texturized surface over which the silicone rubber is placed and cured. In yet another embodiment, the surface is scratched, carved, burned, or etched using ion beam, chemical or other physical techniques to texturize the exterior surface. There is no specific disclosure in the prior art of texturizing material for coating the mandrel or inside of a mold cavity to generate a texturized surface of the exterior of the implant.